The present invention relates to display panels, and more particularly, to liquid crystal display (LCD) panels with anti-Newton ring structures.
As manufacturing costs decrease and quality improves, liquid crystal displays are increasingly employed in different products such as notebook computers, personal digital assistants (PDAs), mobile phones, clocks, and the like. Since liquid crystal displays are passive luminous devices, a back light unit is required for the LCD devices to be seen in the dark.
Typically, LCD devices can be divided into several types according to their display methods. For example, a reflective type LCD device saves power and reduces manufacturing costs by reflecting light from the environment for image display. A trasmissive type LCD device comprises an LCD panel and an additional backlight unit for providing a light source to the LCD panel, leading to higher brightness and less restrictions on use.
FIG. 1 is a schematic diagram of a conventional transmissive LCD device 100. As shown in FIG. 1, the LCD device 100 comprises a display panel 120 mounted on a back light unit 110. The back light unit 110 provides a light source for the display panel 120. The display panel 120 comprises a bottom substrate 130, a top substrate 150, and a liquid crystal layer 170 interposed therebetween. The bottom substrate 130 and the top substrate 150 are both transparent substrates, such as glass substrates. Note that FIG. 1 is a simplified cross-sectional diagram from which some elements on the bottom substrate 130 and the top substrate 150 have been omitted for clarity.
Referring to FIG. 2 and FIG. 3, FIG. 2 shows a schematic diagram of a pixel 122 of the display panel 120 adjacent to a side of the bottom substrate 130 and FIG. 3 shows a cross-sectional diagram along a line A-A′ in FIG. 2. As shown in FIG. 2 and FIG. 3, the bottom substrate 130 is defined with an array region 130A and a display region 130B. As shown in FIG. 3, the display panel 120 comprises a buffer layer 132 disposed on the bottom substrate 130. A silicon layer 134 is formed on the buffer layer 132. The silicon layer 134 is then patterned and only a portion of the silicon layer 134 in the array region 130A is left to serve as an active area having a source 136, a drain 138, and a channel region 137 between the source 136 and the drain 138. The portion of the silicon layer 134 in the display region 130B is completely removed to increase the brightness of the display panel 120 as the silicon layer 134 has a high reflection rate.
Thereafter, at least one gate insulator 142 is formed on the silicon layer 134 and the buffer layer 132. A gate electrode 144 composed of a conductive material is disposed on the gate insulator 142 directly above the channel region 137. The gate 144, the source 136, and the drain 138 form a transistor 140. A dielectric layer 146 is disposed on the gate electrode 144 and the gate insulator 142. A planarization layer 148 is formed on the dielectric layer 146. As previously mentioned, only one pixel is shown in FIG. 2 and FIG. 3 for clarity while the display panel 120 comprises a plurality of pixels arranged in a matrix.
Regarding the top substrate 150, multiple layers comprising a color filter layer, a top electrode and an alignment layer are formed on a bottom side of the top substrate 150. Since the operating mechanism of the display device 100 is known to those skilled in the art, it is not described in detail here.
Although the display panel 120 is a transmissive display panel, light entering the display panel 120 from the external environment is still partially reflected. For example, light is often reflected by the transparent substrates 130 and 150, the dielectric layer 146 disposed on the surface of the bottom substrate 130, and the layers attached to the top substrate 150, such as the color filter layer. After the light beams are reflected, interference from the reflected light beams occurs, leading to a plurality of dark regions and bright regions arranged in a ring type stripe with noticeable differences in brightness, a phenomenon known as a Newton ring phenomenon. This phenomenon seriously deteriorates the display performance of the display panel 120. Thus, a new display panel structure is desirable to solve the aforementioned problem.